Certain substituted benzthiazole-n-oxides and their preparation

ABSTRACT

Novel benzthiazole-N-oxides are obtainable by the reaction of halogenonitrobenzenes additionally activated by one or more electronegative substituents with mercaptomethyl compounds in an inert solvant in the presence of a base in the temperature range of from 20* to 160* C. The new benzthiazole-N-oxides are suitable for use as colored pigments e.g. for dyeing plastics.

United States Patent Wagner et al.

[54] CERTAIN SUBSTITUTED BENZTHIAZOLE-N-OXIDES AND THEIR PREPARATION[72] Inventors: Klaus Wagner; Ernst Roos, both of Cologne, Germany [73IAssignee: Farbenfabriken Bayer Aktiengesellschaft, Liverkus en, Germany[22] Filed: Jan. 29, 1970 [21] Appl. No.: 6,922

[30] Foreign Application Priority Data Jan. 31, 1970 Germany ..P 19 04653.8

[151 3,691,186 [451 Sept. 12,1972

[56] References Cited UNITED STATES PATENTS 3,187,001 6/1965 Meyer et a]..260/304 Primary Examiner-Alex Mazel Assistant Examiner-R. J. GallagherAttorney-Burgess, Dinklage & Sprung [57] ABSTRACT Novelbenzthiazole-N-oxides are obtainable by the reaction ofhalogenonitrobenzenes additionally activated by one or moreelectronegative substituents with mercaptomethyl compounds in an inertsolvant in the presence of a base in the temperature range of from 20 to160 C.

The new benzthiazole-N-oxides are suitable for use as colored pigmentse.g. for dyeing plastics.

10 Claims, No Drawings CERTAIN SUBSTITUTED BENZTl-llAZOLE-N- OXIDES ANDTHEIR PREPARATION This invention relates to novel benzthiazole-N-oxidesand to a process for their production in, which substituted halogennitrobenzenes additionally activated by electronegative substituents arereacted with a compound of the general formula ns-ciu-R in which Rrepresents an-electronegative group, in an inert solvent in the presenceof bases.

Nitrobenzene derivatives of the general formula N; h I

are preferably used as starting products in the process according to theinvention In this formula, X represents a halogen atom, R represents anelectronegativeradical, R represents an electronegative radical, Rrepresents hydrogen or an aliphatic radical and n l or 2.

Suitable halogen atoms (X) include fluorine, bromine, iodine and,preferably, chlorine.

Although the nitro group represents the preferred electronegativeradical (R the groups CP and SO Y are also suitable, Y representing analiphatic, araliphatic or aromatic radical and even an optionallysubstituted amino group. The, group --SO M also represents a suitableelectronegative radical (R,), M representing the equivalent of an alkalimetal (preferably sodium, potassium) or alkaline earth metal (calcium).

In this context, aliphatic radicals (Y) include those containing from 1to 8 and preferably from one to four Araliphatic radicals (Y) containone to four and preferably one or two carbon atoms in the aliphaticchain and as the aromatic radical preferably the phenyl radical. Thephenyl radical represents the preferred aromatic radical (Y).

Where Y represents an optionally substituted amino group, one or bothhydrogen atoms may be replaced by lower alkyl groups or even by fiveorsix-membered cycloaliphatic radicals. The alkyl groups together with thenitrogen atom may form part of a preferably fiveor six-membered ringsystem. In the case of a six-ring, this ring preferably contains anoxygen or sulphur atom as the additional hetero atom, or even a nitrogenatom substituted by a lower alkyl group.

One of the hydrogen atoms of the amino group may optionally also besubstituted by a phenyl radical.

Suitable electronegative radicals (R include not only those mentioned inreference to R with the same scope of meaning, but also the cyano groupand the carbalkoxy radical, in which case the carboxyl group can beesterified not only with an aliphatic or araliphatic alcohol but alsowith a phenol. These radicals have the same scope of meaning as thealiphatic, araliphatic or aromatic radicals (R Aliphatic radicals Rinclude those containing from one to eight, and preferably from one tofour carbon atoms, cycloaliphatic radicals containing five or six carbonatoms in the ring system being mentioned by way of preference.

The electronegative radicals R include preferably carbalkoxy groupsespecially those containing from one to four carbon atoms, and also thecyano group and the radical CO-Z. Z representing hydrogen, an alkoxygroup containing from one to eight and preferably from one to fourcarbon atoms and also an aliphatic, araliphatic or aromatic radical withthe same scope of meaning as that indicated in reference to R Thefollowing represent examples of suitable nitrobenzene compounds:

carbon atoms which optionally may also be branched.

Naturally, aliphatic radicals also include the cycle aliphatic radicals,those containing five or six carbon atoms in the ring system beingpreferred.

Examples of suitable mercapto compounds include inter alia mercaptoacetone, mercapto acetaldehyde, phenacylmercaptan, mercaptoacetonitrile, preferably thioglycolic acid ester.

The process according to he invention is carried out in the presence ofwater and/or organic solvents at temperatures of from 20 to 160C, moreparticularly at temperatures of from 40 to 80C. Examples of suitableorganic solvents include methanol, ethanol, propanol, i-propanol,toluene, dioxan, tetrahydrofuran.

The process is normally carried out by reacting equimolar quantities ofthe corresponding nitrobenzene derivative and the condensation componentin benzene for example at temperatures of from 40 to 80C with somewhatmore than the equimolar quantity by weight of a tertiary base such asfor example trimethyl amine, triethyl amine, tributyl amine, en-

domethylene piperazine or even N,N-dimethylbenzylamine in portions, andstirring the reaction mixture for a while at around 60C.

Some of the novel benzthiazole-N-oxides formed through the reaction areprecipitated during the reaction in the form of yellow to reddish browncrystalline compounds which can be separated off by the usual methodsand after washing with water can be isolated in pure form and in highyields. Where necessary the solvent should be removed in vacuo and thesolid residue obtained treated as described above. In the case of salts(R SO M), the free acids (R S 11) can be obtained in the usual way.

The novel benzthiazole-N-oxides that can be obtained by the processaccording to the invention correspond to the general formula in whichthe radicals have the meanings defined above; where R SO;,M, M can alsorepresent hydrogen.

The claimed process is illustrated by the following general reactionequation in which the radicals are as defined above in other words, thereaction is accompanied not only by elimination of the group X in theform of the corresponding hydrogen halide but also by cyclization withthe nitro group in the o-position to give the benzthiazole-N-oxidederivative.

Some of the benzthiazole-N-oxides that can be obtained by the processaccording to the invention are reproduced in the following T\ft) w l ll'itiHH-llr.

The substituted benzthiazole-N-oxides are suitable for use as yellow,orange or reddish brown pigments for example for dyeing plastics.

EXAMPLEI NC -N 0 \SjC0OC2lI5 45.4 g (0.2 mol) of 2,6-dinitro-4-cyanochlorobenzene and 24 g (0.2 mol) of thioglycolic acid ethyl ester aredissolved in 700 cc of benzene. 22 g (0.2 mol 10% excess) of triethylamine are added dropwise to this solution at 30 to 50C, occasionalcooling with ice water being necessary. On completion of the dropwiseaddition, the reaction mixture is stirred for 3 hours at 50C andfiltered under suction after cooling. The filter residue is washed withwater and dried. 47 g percent of the theoretical) of 2-carbethoxy-5-cyano-7nitrobenzthiazole-N-oxide are obtained in the form of a yellowpowder decomposing at C. For further purification the product can bedissolved in and crystallized from ethylene glycol monoethyl ether.Analysis: C H N O S (293.2)

Calculated: C: 45.1 H: 2.4 O: 27.3 N: 14.3 S: 10.9

Found: C: 45.2 H: 2.8 O: 27.2 N: 14.7 S: 10.8

EXAMPLE 2 K035 --mN-U l (:uuun,

. H l N 02 96 g (0.3 mol) of potassium 4-chloro-3,5- dinitrobenzenesulphate and 36 g (0.3 mol) of thioglycolic acid ethyl ester aresuspended in 750 cc of methanol. 33 g (0.3 mol excess) of triethylamineare then added dropwise and the reaction mixture kept at 60C,occasionally being cooled with ice water. After the triethylamine hasbeen added, the reaction mixture is stirred for 6 hours at 60C. Aftercooling, the yellowish brown crystal paste is filtered under suction andwashed with a little methanol. 5-potassium-2-carbmethoxy-7nitrobenzthiazole-N-oxide sulphonate isobtained in a yield of 75 g (68 percent of the theoretical). For furtherpurification, the product can be dissolved in and crystallized fromwater. Accordingly, transesterification occurs in addition tocyclization in the above reaction.

Analysis: C H N O S K Calculated: C: 29.1 H: 1.5 O: 34.4 N: 7.5 S: 17.2Found: C: 29.1 H: 1.8 O: 33.9 N: 7.8 S: 17.0

EXAMPLE 3 S i COOCzHs 52.0 g (0.2 mol) of 2,6-dinitro-4-carbmethoxychlorobenzene and 24 g (0.2 mol) of thioglycolic acid ethyl ester aredissolved in 600 cc of benzene. 22 g (0.2 mol 10% excess) of triethylamine are added dropwise to this solution at to 60C. After the triethylamine has been added, the reaction mixture is stirred for 2 hours at70C, the triethyl amine hydrochloride precipitated is filtered undersuction after cooling and the benzene distilled off in vacuo.Forpurification, the

. solid residue is dissolved in and crystallized from ethylacetate/dioxan. 2'carbethoxy-5carbmethoxy-7- nitrobenzthiazole-N-oxidemelting at 148C is obtained in a yield of g or 61 percent of thetheoretical. Analysis: C H N O S (326.3)

Calculated: C: 44.2 H: 3.1 O: 34.3 N: 8.5 S: 9.8 Found: C: 44.5 H: 3.2O: 34.2 N: 8.7 S: 9.9

EXAMPLE 4 somu EXAMPLE 5 24.7 g (0.1 mol) of 2,4,6-trinitrochlorobenzene and 12 g (0.1 mol) of thioglycolic acid ethyl ester aredissolved in 300 cc of benzene. 11 g (0.1 mol 10% excess) of triethylamine are added dropwise to this solution at 30 to 50C, occasionalcooling of the highly exothermic reaction with ice water beingnecessary. After the triethyl amine has been added, the reaction mixtureis stirred for 2 hours at 50C. After cooling, the brownish red crystalpaste is suction filtered, the filter residue washed with water and theresidue recrystallized from ethyl acetate. 2-carbethoxy-5,7-dinitrobenzthiazole-N-oxide in the form of brownish yellow crystals isobtainedin a yield of 18 g (52 percent of the theoretical).

Analysis: C,OH N O-,S (313.2)

Calculated: C: 38.4 H: 2.2 O: 35.8 N: 13.4 S: 10.2

Found: C: 39.1 H: 2.9 O: 35.2 N: 13.0 S: 9.7

What is claimed is:

l. Benzthiazole-N-oxides of the formula (Rig/wi wherein R represents acyano group, SO CH or the radical COZ in which Z represents hydrogen, analkoxy group having one to eight carbon atoms, an alkyl radical havingone to eight carbon atoms, a cycloalkyl radical having five to sixcarbon atoms, a phenylalkyl radical with one to four carbon atoms in thealkyl portion or a phenyl radical;

R represents NO CF a group of its formula SO Y wherein Y is the same asZ defined previously and in addition an optionally substituted aminogroup wherein one or both hydrogen atoms can be replaced by alkyl of oneto eight carbon atoms or cycloalkyl of five to six carbon atoms, a groupof the formula -SO M in which M represents hydrogen or the equivalent ofan alkali or alkaline earth metal;

R represents hydrogen, a cyano group, carboalkoxy radical having one toeight carbon atoms, NO CF Cl, a group of the formula SO Y wherein Y isas defined previously, or a group of the formula SO M in which Mrepresents hydrogen or the equivalent of an alkali or alkaline earthmetal;

R represents hydrogen or alkyl having one to eight carbon atoms orcycloalkyl having five to six carbon atoms; and n represents 1 or 2.

2. 2-carbethoxy-5-cyano-7-nitro-benzthiazo1e-N-oxide.

3. Potassium 2-carbomethoxy-7-nitro-benzthiazole- N-oxide-S-sulphonate.

4. 2-carbethoxy-5carbomethoxy-7-nitrobenzthiazole-N-oxide.

5. Sodium 2-carbethoxy-5-nitro-benzthiazole-N- oxide-7-sulphonate.

6. 2-carbethoxy-5,7-dinitro-benzthiazole-N-oxide.

7. A process for the production of benzthiazole-N- oxides, wherein asubstituted halogenonitrobenzene having the general formula in which Xrepresents a halogen atom:

R represents NO CF a group of its formula SO Y wherein Y is the same asZ defined previously and in addition an optionally substituted aminogroup wherein one or both hydrogen atoms can be replaced by alkyl of oneto eight carbon atoms or cycloalkyl of five to fix carbon atoms, a groupof the formula SO M in which M represents hydrogen or the equivalent ofan alkali or alkaline earth metal;

R represents hydrogen, a cyano group, carboalkoxy radical having one toeight carbon atoms, NO CF -Cl, a group of the formula SO Y wherein Y isas defined previously, or a group of the formula --SO M in which Mrepresents hydrogen or the equivalent of an alkali or alkaline earthmetal; R represents hydrogen or alkyl having one to eight carbon atomsor cycloalkyl having five to six carbon atoms; and n represents 1 or 2.is reacted with a mercaptomethyl compound of the general formulaHS-Cl-h-R in which R represents a cyano group, -SO CH or the radical--COZ in which Z represents hydrogen, an alkoxy group having one toeight carbon atoms, an alkyl radical having one to eight carbon atoms, acycloalkyl radical having five to six carbon atoms, a phenylalkylradical with one to four carbon atoms in the alkyl portion or a phenylradical, in an inert solvent in the presence of a base at temperaturesfrom 20 to C.

8. A process as claimed in claim 1 wherein the inert solvent is waterand/or an organic solvent.

9. A process as claimed in claim 7 wherein the mercapto-methyl compoundis mercapto-acetone, mercapto-acetaldehyde, phenacyl mercaptan,mercaptoacetonitrile or thioglycolic acid ester.

10. A process as claimed in claim 7 wherein the base is trimethylamine,triethylamine, tributylamine, endomethylene piperazine orN,N-dimethylbenzylamine.

I 'Farben 1730s 'PO-1050 UNITED STATES PATENT OFFICE t 69 CERTIFICATE OFvcommcrmw Patent No. 3,691,186 DatedjeptembeflZr 1972 Inventor(s) KLAUSWAGNER and ERNST ROO S It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Front Page, under "Foreign Application Priority Data? 17.1970" .shouldread 1969 Col. 2, line 33, "Z.Z" should read 'Z,Z"

Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents v I I Iv PO-1 ,UNITED STATES PATENT OFFICE 1 r CERTIFICATE OFCORREQTIGN Patent No. 3,691,186 Dared S eptember 12.. 1972 Inventor(s)KLAUS WAGNER and ERNST ROOS It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Front Page, under "Foreign Application Priority Data" '1 970" .shouldread 1969 Col. 2, line'33, "2.2" should read "2,2"

Signed and sealed this 6th day of March 1973.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.PLETCHER,JR.

Commissioner of Patents Attesting Officer I

2. 2-carbethoxy-5-cyano-7-nitro-benzthiazole-N-oxide.
 3. Potassium2-carbomethoxy-7-nitro-benzthiazole-N-oxide-5-sulphonate. 4.2-carbethoxy-5-carbomethoxy-7-nitro-benzthiazole-N-oxide.
 5. Sodium2-carbethoxy-5-nitro-benzthiazole-N-oxide-7-sulphonate. 6.2-carbethoxy-5,7-dinitro-benzthiazole-N-oxide.
 7. A process for theproduction of benzthiazole-N-oxides, wherein a substitutedhalogenonitrobenzene having the general formula in which X represents ahalogen atom: R1 represents -NO2, -CF3, a group of its formula -SO2Ywherein Y is the same as Z defined previously and in addition anoptionally substituted amino group wherein one or both hydrogen atomscan be replaced by alkyl of one to eight carbon atoms or cycloalkyl offive to fix carbon atoms, a group of the formula -SO3M in which Mrepresents hydrogen or the equivalent of an alkali or alkaline earthmetal; R2 represents hydrogen, a cyano group, carboalkoxy radical havingone to eight carbon atoms, -NO2, -CF3, -Cl, a group of the formula -SO2Ywherein Y is as defined previously, or a group of the formula -SO3M inwhich M represents hydrogen or the equivalent of an alkali or alkalineearth metal; R3 represents hydrogen or alkyl having one to eight carbonatoms or cycloalkyl having five to six carbon atoms; and n represents 1or
 2. is reacted with a mercaptomethyl compound of the general formulaHS- CH2- R in which R represents a cyano group, -SO2CH3, or the radical-CO-Z in which Z represents hydrogen, an alkoxy group having one toeight carbon atoms, an alkyl radical having one to eight carbon atoms, acycloalkyl radical having five to six carbon atoms, a phenylalkylradical with one to four carbon atoms in the alkyl portion or a phenylradical, in an inert solvent in the presence of a base at temperaturesfrom 20* to 160*C.
 8. A process as claimed in claim 1 wherein the inertsolvent is water and/or an organic solvent.
 9. A process as claimed inclaim 7 wherein the mercapto-methyl compound is mercapto-acetone,mercapto-acetaldehyde, phenacyl mercaptan, mercapto-acetonitrile orthioglycolic acid ester.
 10. A process as claimed in claim 7 wherein thebase is trimethylamine, triethylamine, tributylamine, endomethylenepiperazine or N,N-dimethyl-benzylamine.